Ok, are you in the house now? Is he?
Can you either go somewhere with the children - to your mum's? - or get someone to come and be with you?
Or, there is the option of going to a refuge. Wiser and more experienced people will be along shortly who can advise you here, I have read on here that they are NOT scary bleak places- quite the opposite. Can you also ring WA too, regardless of tonight's plans, and get some advice?
Also - phone police? Report a DV incident at the home and they will put a mark next to your address.
That's short term - get hold of someone in RL to give you some support and to be with you and the kids, report (if you can) as a safety precaution, and get away from him if you can, as soon as possible.
Long term - IT WILL BE OK. You are NOT a fool - you are a normal person, one with a conscience and a sense of responsibility that makes you think, ok, I really must try this, and this, and this, before I make permanent changes that will impact on the kids'. Don't worry, don't beat yourself up. It's what people do. Forget the flat - the landlord let you down - good thing you didn't move in eh!
If you were going to be able to rent a place independently anyway, and if there is nowhere you could stay short-term until you can now move, I would go to a refuge, and from there, sort out a new flat. WA could help you in this I'm sure. If you have someone you can go to, make arrangements to go there and sort out a new flat from there.
Others with wiser words will be along soon...
Good luck, you will be ok, you were almost out, you gave it one last chance, now you know you'll definitely be out. You are strong.